At least 25 people died in a huge explosion in Lebanon capital Beirut on Tuesday, Reuters reported. Videos showed a large mushroom cloud over the city, after a blast so strong that the earth shook.

More than 2,500 people have been injured. The toll and number of injuries are likely to rise.

Interior Minister Mohammed Fahmi said it was likely that ammonium nitrate being stored in a warehouse at the port caused the blast, reported Al Jazeera.

There was speculation about a second explosion as well. The second explosion may have been at the Hariri residence in the city, according to BBC.

Videos reportedly showed people trapped under the rubble as fire services personnel conducted rescue operations.

Windows across the city were shattered by the impact of the explosion, and many buildings were damaged.

Prime Minister Hassan Diab announced a day of national mourning on Wednesday, reported AFP.

Lebanon’s Health Minister Hamad Hassan instructed all hospitals around the neighbourhood to be prepared to treat the injured. However, AFP said that hospitals in Beirut were turning away people “with blood streaming down their faces because they’re too full or damaged to take them in”.

Al Jazeera reporter Zeina Khodr spoke of “chaos in the streets”. “I was kilometres away, the glass broke everywhere around me,” Al Jazeera quoted her as saying.

Buildings as far away from the explosion spot as 10 km were damaged, reported CNN. This included former Prime Minister Saad Hariri’s headquarters.

The blast came a day ahead of a court verdict in the trial connected with the killing of former Prime Minister Rafik Hariri. A tribunal of the United Nations is expected to give its verdict in the case of Hariri’s death in 2005, which involves four suspects.

The incident also came amid political turmoil in Lebanon, where there have been protests against the government’s management of the worst economic crisis since the 1975-1990 civil war. Besides this, there have also been reports of tension along the border with Israel as well, according to BBC.